Do You Need to Know Dive Tables when Using a Dive Computer

Though scuba may be advertised to the general public as a fun and laid-back sport, it can actually be extremely complicated. There is a vast amount of knowledge that you have to memorize and learn to understand, which can be difficult.  Memorizing all of this knowledge may at times seem overwhelming and even useless, but doing so is essential when it comes to ensuring your own safety. As well as memorizing a lot of important facts and safety tips, you also have to get to know your equipment.  

Equipment is crucial to your scuba diving experience, in fact, your equipment is what protects you from your surroundings and keeps you safe in unfamiliar territory. Every year scuba equipment becomes much more advanced, and brand new items are constantly introduced into the market, with the promise of making your scuba diving experience much easier. 

Scuba diving has been around for decades, and as the decades have gone on, technology has only become more complex and advanced. In life away from scuba, this has been seen in our phones and TVs, but in scuba, this has been seen through the introduction of brand new and exciting equipment.  

The world of scuba has really changed over the years, in fact, some of the equipment that scuba divers cannot live with is quite new in comparison to the other equipment. This includes items such as full-face dive masks and even dive computers. You may be surprised to learn that dive computers are a relatively recent addition to the vast list of scuba diving equipment due to just how important they are in keeping a scuba diver safe. Though this may be surprising, it is also important to imagine what technology was really like in the mid-1900s, where something as complex as a dive computer simply wouldn’t be viable. You may be wondering how people successfully completed a scuba trip without the help of a dive computer. Before introducing the dive computer, people used these things called dive tables- but what exactly are dive tables? 

 

What are dive tables? 

Dive tables are used as a means to determine how long you can safely be submerged in the water, depending on the depth, for the subsequent and initial dives. At first glance, dive tables can look extremely intimidating and confusing, so there is no wonder why an alternative was created.  Becoming a scuba diver isn’t all about trying to stay fit while diving, you also need to have a good grasp of safety procedures and an understanding of descending depths.  Because of this, before you can even complete a PADI diver course, you first need to be able to understand a dive table. This shows that even though there are new technologies available to help you with your own safety, it is still important that you are able to understand it yourself.  

This is because technology isn’t always reliable and can give in at really any point, so knowing how to map your own safety is a key scuba diving skill. 

However, there are some limitations when it comes to dive tables. They are created with the assumptions that the diver will remain at the same depth throughout the entire scuba trip, which seems completely improbable. When you explore the ocean’s depths, you can understandably drift and find yourself at different depths. However, when you are using a dive table as a source of calculations, it is key that you remain at the set depth, as the dive table also calculates your nitrogen absorption.  

Knowing your nitrogen absorption is key when trying to combat one of the most dangerous conditions that you can face as a scuba diver, this is decompression sickness.  

What is decompression sickness? 

Decompression sickness, also known as the bends, is caused when rapid decompression leads to a build-up of nitrogen bubbles in the blood and tissue. Decompression sickness can be extremely inconvenient and also painful. It also has a list of nasty side effects, such as pain in the muscles and joints as well as terrible nausea. Though those symptoms are hard to deal with, arguably the worst symptom of all is potential paralysis. After all, the last thing you want when you are diving is losing control of your own body’s movements. Decompression sickness is the reason that dive tables were put into practice in the first place, as it was becoming a very common and very dangerous problem.

The fact that they are so important when it comes to maintaining your safety is another reason that you should know how to read them, as being able to plan your trip could prevent any possible bends from occurring. 

How to read a dive table 

For your standard recreational dive planner, you will be able to work out just how long you will be able to enjoy your drive without having to stop several times for decompression stops.  If you are someone that isn’t very strong in the field of maths, trying to understand how to read a dive table can be very overwhelming at first glance. 

However, one way in which reading the dive table has been made easier is through pressure groups aimed at repetitive diving.   

Pressure groups 

When you do your first dive, you should be able to work out what pressure group you fall under. This is worked out by looking at your tank’s 02 percentage and comparing it with the depth you are diving to. You then look at the depth you will be driving to and compare it to the time you will be diving for. For example, if you were diving to 70 feet for around 30 minutes, you would fall into pressure group I. 

Calculating your pressure group for your second dive depends on remembering the details of your first dive. On top of this, you also need to remember your surface intervals, which will indicate the nitrogen levels that are still in your body. Working this out will allow you to know just how long you can stay in the water before it becomes unsafe.  

Repetitive dive 

If you are using a dive table and plan on doing a repetitive dive, you have to try and work out your residual nitrogen time, also known as RNT. As previously discussed, this is the nitrogen you have leftover in your body from your previous dive. This completely depends on looking at the results of your first dive and taking into account your initial pressure group. If this is your third or fourth dive, it is crucial that you try your best to accurately log your numbers as you will have to make changes to your dive. For example, you will have to alter the time you spend in the water and work out new decompression stops or even introduce them if you didn’t use them in your previous dive.  

Dive computer 

A dive computer works in a different and more accurate way. As previously discussed, a dive table will only work on the assumption that you will be staying at the same depth for your entire dive trip, which we know will likely not be the case. A dive computer records an accurate time and depth that a scuba diver has reached during their dive, and they will use this to accurately calculate the level of nitrogen absorption that has actually occurred. This newfound accuracy that has come with the use of dive computers means that people can spend even longer under the water during their dive. It also means that people can take shorter surface intervals as in the past, people have had longer surface intervals due to inaccurate results just to be safe.  

 

Do you need a dive table when you are using a dive computer?  

Now, you don’t necessarily have to use a diver table if you have access to a dive computer. In fact, if you were to scuba dive in Florida, if you’re a beginner, you wouldn’t be asked to use a dive table during your first diving experience. This is because it takes quite a long time to understand dive tables, so if you are only doing diving for a holiday experience, you will not be required to learn how to read the dive tables.  

Dive computers work in a way that is much more accurate than your standard dive table, because of this, you are not required to use a dive table during your scuba trips. However, it is still recommended that you learn how to read a dive table if you are serious about pursuing scuba diving as a hobby. 

Reasons why you should learn how to read a dive table 

If you are someone that is not convinced that learning how to read a dive table is worth your while, you may require more reasons as to why you should pick it up as a skill. 

 

Technology is unreliable  

Though technology is amazing and extremely useful in our day-to-day lives, it is also extremely unreliable.  If you go scuba diving, you will not likely take more than one dive computer with you. After all, they cost quite a bit in some cases, so it wouldn’t make sense to have several. Technology is also extremely temperamental, and you could enter the water with your dive computer being in perfect working order, then ten minutes later, it has completely broken.  

 If this was the case and you were already in the water, you could find yourself in a difficult situation. Dive computers don’t give you immediate estimates for your entire dive, in fact, you keep up to date with your stats by constantly checking the computer. If it was to break and you hadn’t checked it in a while, you could find yourself in an extremely difficult place. However, if you had worked out your timing for a dive table, then you would be in a better position.  

Even if you don’t choose to follow your dive table timings down to the exact details, you would still be in a better position than if you didn’t use a dive table at all. Keeping yourself safe should be your main priority when you are scuba diving, so why not take the additional steps to ensure that you are as safe as you possibly can be.  

Expense  

As I have previously discussed, dive computers can actually be extremely expensive. You can go to some places and find a dive computer at a decent price, but you can still expect to pay way over five hundred dollars for a quality diver computer. If you take this into account, along with all of the other bits of equipment that you need to buy, this can make your hobby super expensive.  

Obviously, you can’t exactly cut out the cost of things such as oxygen tanks. However, you can cut back on items that you don’t necessarily need. You don’t necessarily need a dive computer if you know how to accurately read and also follow a dive table, after all, people were diving without dive computers for quite some time. It is also an extremely useful skill to have anyway, and not owning a dive computer in the first place will only encourage you to really improve your ability to read dive tables.  Compare it with learning how to drive, just because you can first learn how to drive with an automatic doesn’t mean you necessarily should, as you will only be putting yourself at a disadvantage. 

Company  

If you plan on diving with a group of people and have the same oxygen levels and route, you could be ok not using a dive table in the unlikely event your drive computer breaks, as you will be able to get an idea of timing stats from them.